I think my fuel pump is weak on 1997 Civic with 375k miles

I have a 97 civic I bought new now with a whopping 375k miles on it.

When I start the car I often don’t hear as much noise from the fuel pump as I used to. But, often it is the same. After the car has been off for a half hour or so, after about 2 minutes of driving it loses power, but then it comes back fine.

I suspect weak fuel pump. I’d like to try the repair myself.

Proper diagnosis for a proper repair.Can you narrow down failures for a proper diagnosis?

Doesn’t sound like a fuel pump to me.

I could try to measure the pressure. I haven’t done it yet but have seen youtubes on it… the reason I suspect the pump is (I forgot to mention) when it loses power, it’s generally up a little hill. So, when a load is on. But then, it seems to recover. I guess the filter could be clogged, but I had a shop put a new one on. It should be good unless they left the old one on, which is not impossible.

Does this have OBDII?
You can check for high positive fuel trim numbers.
I would also check valve lash.

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Thanks. I did check the fuel/trim, and it is definitely high. If in neutral, like 10. If I put it in drive, it shoots up to like 40!

I had the valves adjusted by a pro a couple of years ago. I did check myself, and they seem OK.

I forgot to mention, that the fuel trim seems normal at highway speed but goes up on idle.

At 375k it could be lots of things. Have you checked compression? Valve adjustment?

I used to take my car out at night testing it with the fuel pressure gauge taped to the windshield. Testing pressure is really the only way to test the pump except for testing volume. I suspect though that there is more than the fuel pump that might be weak.

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Clogged fuel filter, vacuum leak come to mind

You might have a rusted fuel line under the car. My 1999 Civic needed this replaced a couple years ago. Symptom was fuel smell, no running issues, but in time there would been or maybe a fire. 200,000 miles + and going strong.

I wish I had an idea of what the problem could be…….but

WOW !!! I had no idea a fuel pump could last 375,000 miles.
I would have lost my nerve and replaced it at 200,000 miles.

I feel like my best course of action is to test the pressure first. I will watch some youtubes on it. I have a feeling it is the pump though since it sounds quieter often when I prime the key forward in starting, and it loses power up a hill in the first minutes of driving.

The car has low compression in number #1. I get only 80 PSI or so. The rest are all over 100 PSI. The engine is surprisingly powerful still, once warmed up!

I suppose the relay might not be sourcing enough current. The relay is a couple of years old though.

I guess maybe 150k or so is highway miles

That low compression number leads me to believe this car has one wheel in the grave and the other three wheels on banana peels.

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Here is an interesting guide on fuel pumps`. Also regarding your compression issue, if you take a teaspoon of oil and place it into the suspect cylinder what happens to your compression? If it increases you know you have a ring sealing issue and there may be somethings you could try to clean up possible carbon on your rings that is causing the problem.

As far as fuel trims go, they are very unique to all vehicle makes and models. The reason you see the fuel trims change from idle, to in gear and than when driving down the highway is that they operate in different cells depending on conditions such as engine load, speed, rpm, etc. Think of the cells as a spreadsheet, this spreadsheet stores long term fuel trims for each condition. Depending on what is occurring the PCM will decide which cell to obtain long term fuel trim data from. It will than try to zero out your short term fuel trims by adjusting your long term. You are really concerned about your long term fuel trims in this situation.

Have you checked fuel pressure? Do you have access to a lab scope?

P.S Welcome to the community!!

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Yep, low compression = worn out engine. ‘over 100’ isn’t good, it’s less bad. How far over 100?

I got 120 across the board

When a mechanic adjusted the valves a couple years ago, he said, yes, rings bad. I kept driving it anyway, since a mechanic has been telling me to get rid of it now for around six years annually.

Check the fuel pressure, if it’s good, drive on until it won’t drive no mo.